Shuihua Tang

Supercapacitive behavior of an asymmetric supercapacitor based on a Ni(OH)2/XC-72 composite

A Ni(OH)2/Vulcan XC-72 (XC-72) composite has been synthesized by a microwave assisted method; it demonstrated a high specific capacitance of 1560 F g−1 at 1 A g−1 with carbon nanotubes as conductive agents. Ni(OH)2/XC-72, activated carbon (AC) and non-woven fabric were, respectively, used as a positive electrode, a negative electrode and a separator to assemble an asymmetric supercapacitor. This AC//Ni(OH)2/XC-72 supercapacitor achieves a remarkable capacitance of 92.2 F g−1 at a current density of 0.5 A g−1, a maximum energy density of 36 W h kg−1 and a power density of 490 W kg−1 based on an active material in a 6 M KOH aqueous electrolyte with a negative/positive electrode mass ratio of 1.75 within a voltage window of 1.6 V. Furthermore, the capacitance of the unit supercapacitor remains 85% after 1000 charging–discharging cycles. These results indicate that the AC//Ni(OH)2/XC-72 supercapacitor is promising to be applied in a practical device for energy storage.

High supercapacitive performance of Ni(OH)2/XC-72 composite prepared by microwave-assisted method

A 60 wt% Ni(OH)2/XC-72 composite was synthesized via a facile and rapid microwave-assisted method in an ethylene glycol medium. Transmission electron microscopy images show that Ni(OH)2 is uniformly dispersed on XC-72 and that when carbon nanotubes (CNTs) are added as a conductive agent, they construct a three-dimensional (3-D) network together with the Ni(OH)2 particles and XC-72. The composite demonstrates a specific capacitance of 1296 F g−1 at a scan rate of 2 mV s−1 and 1560 F g−1 at a current density of 1 A g−1 in 6 M KOH aqueous solution, and its retention of specific capacitance is 71% after 1000 cycles. This can be attributed to XC-72 being an excellent support and CNTs with high aspect ratio and good conductivity to construct a 3-D conductive network. This excellent electrochemical performance makes the Ni(OH)2/XC-72 composite promising as an electrode material for a supercapacitor.

Effect of methanol concentration on oxygen reduction reaction activity of Pt/C catalysts

Abstract The oxygen reduction reaction (ORR) activity of Pt/C catalysts was investigated in electrolytes of 0.5 mol/L H2SO4 containing varying concentrations of methanol in a half-cell. It was found that the ORR activity was improved notably in an electrolyte of 0.5 mol/L H2SO4 containing 0.1 mol/L CH3OH as compared with that in 0.5 mol/L H2SO4, 0.5 mol/L H2SO4 containing 0.5 mol/L CH3OH, or 0.5 mol/L H2SO4 containing 1.0 mol/L CH3OH electrolytes. The same tendency for improved ORR activity was also apparent after commercial Nafion® NRE-212 membrane was hot-pressed onto the catalyst layers. The linear sweep voltammetry results indicate that the ORR activities of the Pt/C catalyst were almost identical in the 0.5 mol/L H2SO4 + 0.1 mol/L CH3OH solution before and after coated with the Nafion® membrane. Electrochemical impedance spectroscopy results demonstrated that the resistance of the Nafion® membrane is smaller in the electrolyte of 0.5 mol/L H2SO4 + 0.1 mol/L CH3OH than in other electrolytes with oxygen gas feed. This exceptional property of the Nafion® membrane is worth investigating and can be applied in fuel cell stacks to improve the system performance.

Facile Preparation of Layered Ni(OH)2/Graphene Composite from Expanded Graphite

1 State Key Lab of Oil and Gas Reservoir Geology & Exploitation, Southwest Petroleum University, Chengdu 610500, China. 2 School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, P R China 3 School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500, P R China 4 Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim 7491, Norway. #: with identical contributions * E-mail: spraytang@hotmail.com, geir.martin.haarberg@ntnu.no